Generally, a conventional WLAN adopts a thin AP architecture formed by an AP and an AC. Under such a thin AP architecture, the AC manages the AP in a unified way through a Control And Provisioning of Wireless Access Points Protocol (CAPWAP). As shown in FIG. 1, FIG. 1 is a networking diagram of a WLAN under a thin AP architecture in the related art, and the dotted line in FIG. 1 represents the CAPWAP.
CAPWAP defines two bases for judging an offline state of the AP by the AC. When one of the two bases is met, the AC can determine that the AP is offline.
1. The AC sets a heartbeat keep-alive timer, and determines that the AP is offline if a keep-alive message is not received from the AP within a keep-alive period.
2. After transmitting a request message, the AC needs to retransmit the request message before receiving a response message. A retransmission interval is initially 3 s, and is doubled after retransmission of each time. Moreover, a maximum retransmission interval does not exceed a half of the heartbeat keep-alive period, and the maximum number of retransmission times is 5. The AC determines that the AP is offline if the response message returned by the AP is not received after the request message transmitted by the AC is retransmitted.
In addition, the CAPWAP also defines a basis for judging an offline state of the AC by the AP.
Before a response message of a request message transmitted by the AP is received, the request message needs to be retransmitted. A retransmission interval is initially 3 s, and is doubled after retransmission of each time. Moreover, a maximum retransmission interval does not exceed a half of a heartbeat keep-alive period, and the maximum number of retransmission times is 5. The AP determines that the AC is offline if the response message returned by the AC is not received after the request message transmitted by the AP is retransmitted.
The AC deletes a connection with the AP after determining that the AP is offline. The AP deletes a connection with the AC after determining that the AC is offline. Under the two conditions, the AP can normally work only after re-accessing the AC. A process of re-access of the AP to the AC generally takes a few minutes. During this period, the AP cannot provide a service for a wireless user.
It can be seen from the above that, in a related art, the messages transmitted by the AP and the AC may be delayed or lost under the condition of link quality reduction or instability, and the AP will frequently get offline due to the detection of a keep-alive message or the retransmission response message within only one heartbeat keep-alive period. After getting offline, the AP can normally work only after re-accessing the AC, and the process of re-access of the AP to the AC probably will take a few minutes and even more. If frequently getting offline, the AP will be unavailable, which causes serious impact on user experiences.